Production of nitrites.



FRITZ norms, or DESSAU," GERMANY, ASSIGNQB TQ ELEKTBOGHEMISGHE WERKE,

I G- 1 E- 3 1 O B ERFELD, ERMA BIQDUCTION OF NITRITES.

I No Drawing.

Patented Aug. 12,1913.

To all whom it may concern Beit known that I, Fnrrz ROTHE, a subject of the King of Prussia, and resident of Dessau, Germany, 116 Albrechtstrasse, have invented certain new and useful Improvements in the Production of Nitrites; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as- Will enable others skilled in the art to which it appertains to make and r into nitrites of a high grade of purity, in

use the same.

It is well known that pure solutions of nitrites may be obtainedby the introduction of nitrous gases which contain a slight excess of NO with respect to NO,, into a concentrated solution of alkalis, carbonates of the alkalis, etc., in the absence of air; see G-melin-rKraut H andbuoh der Amrgam'scken Ghemz'e, 7th ed. Vol. II, Part I, page 303.

If, however, the nitrous gases contain air, the conditions of absorption are more complicated, as has been shown by Le Blane (Zeitschrift for Elelctrochemz'e, Vol. XII,

pages 543, 544, year 1906), andin such cases, in addition to nitrites, nitrates are produced in considerable quantities.

Particularly, in the oxidation of nitrogen in the electric furnace such nitrous gases complicating the conditions are produced, inasmuch as it is not feasible to treat these gases with alkali at exactly the time when the oxidation of a portion of the NO 'to N0 has proceeded so far that there formation of pure nitrite NO-|NO,,:N,O,)

is at hand the molecular mixture .of NO+NO :N,,O necessary for the production of pure nitrites. German Patent No. 188188 proposes to avoid these difficulties by cooling down the nitrous gases produced in the electric furnace only to such a degree (300 C.) that at this temperature a further chemical combination of oxygen beyond the-ratio N :O shall not take place. Nevertheless, even the process of the German patent referred to does not completely remove the ditliculties. In practice, where it is a question of obtaining as great a quantitative absorption of the nitrous gases as possible, and as complete a neutralization of the absorption medium as possible, there is always required a number of absorbers in communication with each other. The favorable conditions obtained in the process of the Germanwpatent referred to exist only in the first absorption apparatus, or in a 5 portion of the first absorption apparatus,

whereas further on, in consequence of further diminution of temperature, the composition of the gases constantly diminishes in favor of N0 and the formation of nitrate correspondingly increases; see Foerster & Blich, Zez'tschrift fair Angewamife Oiled/Lie, year 1910, page 2017.

By means of the present invention it is possible, in a simple manner, to convert nitrous gases with almost quantitative output so far as nitrate salts are concerned.

The rocess consists in conveying to the absorption plant, the nitrous gases that are to be absorbed (for instance, the nitrous gases from the electric furnace) ,in two or more separate gas currents, converting a part of these gas currents b approprlate treatment (6. g., cooling su cient time of reaction, etc.) principally into N0 whereas for the other part, by maintaining suitable temperatures and providing the shortest possible path of travel from the electric .furnace'to the absorption apparatus, the formation of N0 is prevented, or any NO present is reconverted into NO, whereupon the said gas currents, immediately before enterin the absorbing medium, are so commingle' that at every portion of the absorption system the ratio NO N0 1:1 exists, or even in some cases, a slight excess of NO is present.

In order to realize the conditions for the the gas containing NO should be mixed not merely at one place with theportion containing N0 but, corresponding to. the pro- -gressive absorption, the gas containing NO should be introduced at different parts of the apparatus where the absorbers'are connected up in series, for instance, in each individual absorber of the series in accordance with the quantity of NO present therein; or, where a single large absorber is employed, at various places in said single large absorber. In carrying out the operation, it is desirable, atsuitable parts of the absorption system, to work with a small excess of NO for the reason that by so doing, the formation of pure nitrite is assured.

In practice, the process has the great advantage that all of the nitrous gases can be converted into nitrite, whereas heretofore, the so-called residual gases given off from the nitrite absorption apparatus haveonly been recoverable by further absorption, by means of lime and the like, in the form of a less valuable mixture of nitrate and nitrite.

The following will serve as an example of the practice of the invention: If the nitrous gases coming, for instance, from an electric air combustion furnace, are first cooled and then introduced into alkali solutions, 6. g.-, into soda-lye, there will be produced in the lye, mixtures of nitrite and nitrate, in which the ratio of the nitrite to the nitrate may vary within wide limits, and, under favorable conditions will show 90 per cent. nitrite. If now, only a ortion of the gases is cooled, this being e ected by giving said portion suflicient time to traverse a suflicient length of conducting pipes, all of the N O or N 0 in said portion will be converted into NO before entering the absorption apparatus. The other portion of the gas, which is cooled only to somewhat less than a dark red heat, is conducted along the shortest path of travel and enters the absorption apparatus through the same gas inlets which are provided for the first portion. The resulting lyes contain from 97 to 99 per cent. nitrite and 3 to 1 per cent. of nitrate. It Will, of course, be understood that the process is likewise applicable to nitrous gases of other ori in containin air or oxygen.

aving thus escribed my invention, what I claim is:

1. In the production of nitrites from nitrous gases containing air or oxy en by absorption in an alkaline medium, tie method of increasing the quantitative yield of nitrites, which consists in subdividing the current of gases to be absorbed into separate gas currents on the way from the place of production to the absorbing medium, and so regulating the conditions of time and temperature in the respective subdivided gas currents that the nitrous constituents in one portion will be delivered into contact with the absorbing medium substantially as NO and the nitrous constituents in the other portion will be delivered into the absorbing medium substantially as NO, the said gas currents being again 'commingled in such manner that at the moment of absorption a sufiicient quantity of NO is present to satisfy the molecular ratio of NO+NO :N O Substantially as described.

2. In the production of'nitrites from nitrous gases containing air or oxygen by absorption in an alkaline medium, the method of increasing the quantitative yield of nitrites, which consists in subdividing the gas currents on the Way from the place of production to the absorbing medium, and so regulating the conditions of time and tem perature in the respective subdivided gas currents that the nitrous constituents in one portion will be delivered into-contact with the absorbing medium substantially as NO and the nitrous constituents in the other por tion will be delivered into the absorbing medium substantially as NO, the said gas currents being again commingled in such manner that at the moment of absorption a sufficient quantity of NO is present to satisfy the molecular ratio of NO+NO :N O and to be slightly in excess; substantially as described.

3. In the production of nitrites from the hot nitrous gases, containing air or oxygen, of an electricfurnace, by absorption in an alkaline medium, the method of increasing the quantitative yield of nitrites, which consists in subdividing the hot gases into separate gas currents, converting the nitrous constituents present in one ortion of said currents substantially into'N 2 by sufiiciently cooling said portion and prolonging its, period of travel from the furnace to the absorbing medium, maintaining a temperature in the other portion of said gas currents on its transit to the absorbing medium suflicient to deliver its nitrous constituents thereinto substantially as NO, and again commingling the gas currents in such'manner that at the moment of absorption a molecular ratio of NO+NO :N O is present throughout said medium; substantially as described.

In testimony whereof I afiix my signature, in presence of two witnesses.

FRITZ ROTHE.

Witnesses EDUARD Horr, ERNEST H. L. MUMMENnorF.

current of gases to be absorbed into separate 

